7-[2-[4-(6-fluoro-3-methyl-1,2-benzisoxazol-5-yl)-1-piperazinyl]ethyl]-2-(1-propynyl)-7H-pyrazolo-[4,3-E]-[1,2,4]-triazolo-[1,5-C]-pyrimidin-5-amine

ABSTRACT

The compound having the structural formula I 
                         
or a pharmaceutically acceptable salt thereof, is disclosed, as well as its use in the treatment of central nervous system diseases, in particular Parkinson&#39;s disease, Extra Pyramidal Syndrome, restless legs syndrome and attention deficit hyperactivity disorder, pharmaceutical compositions comprising it, and combinations with other agents.

This Application claims the benefit of U.S. Provisional Application No.60/720,027 filed Sep. 23, 2005.

FIELD OF THE INVENTION

The present invention relates to7-[2-[4-(6-fluoro-3-methyl-1,2-benzisoxazol-5-yl)-1-piperazinyl]ethyl]-2-(1-propynyl)-7H-pyrazolo-[4,3-e]-[1,2,4]-triazolo[1,5-c]pyrimidin-5-amine,an adenosine A_(2a) receptor antagonist, the use of said compound in thetreatment of central nervous system disorders including movementdisorders, e.g., Parkinson's Disease, Extra-Pyramidal Syndrome, restlesslegs syndrome, essential tremor and Huntington's Disease; attentiondisorders, e.g., attention deficit hyperactivity disorder, cognitiveimpairment and negative symptoms of schizophrenia; and to other centralnervous system diseases such as depression, stroke and psychoses. Theinvention also relates to pharmaceutical compositions comprising saidcompound.

BACKGROUND

Adenosine is known to be an endogenous modulator of numerousphysiological functions. At the cardiovascular system level, adenosineis a strong vasodilator and a cardiac depressor. In the central nervoussystem, adenosine induces sedative, anxiolytic and antiepilepticeffects. In the respiratory system, adenosine inducesbronchoconstriction. In the renal system, it exerts a biphasic action,inducing vasoconstriction at low concentrations and vasodilation at highdoses. Adenosine acts as a lipolysis inhibitor on fat cells and as anantiaggregant on platelets.

Adenosine action is mediated by the interaction with different membranespecific receptors which belong to the family of receptors coupled withG proteins. Biochemical and pharmacological studies, together withadvances in molecular biology, have allowed the identification of atleast four subtypes of adenosine receptors: A₁, A_(2a), A_(2b) and A₃.A₁ and A₃ receptors inhibit, while A_(2a) and A_(2b) receptors stimulatethe activity of the enzyme adenylate cyclase. Analogs of adenosine ableto interact as antagonists with the A₁, A_(2a), A_(2b) and A₃ receptorshave also been identified.

Selective antagonists for the A_(2a) receptor are of pharmacologicalinterest because of their reduced probability of potentiating sideeffects. In the central nervous system, A_(2a) antagonists can haveantidepressant properties and stimulate cognitive functions. Moreover,data has shown that A_(2a) receptors are present in high density in thebasal ganglia, known to be important in the control of movement. Hence,A_(2a) antagonists can improve motor impairment due to neurodegenerativediseases such as Parkinson's disease, senile dementia as in Alzheimer'sdisease, and psychoses.

Adenosine A_(2a) receptor antagonists have been disclosed as beinguseful in the treatment or prevention of Extra Pyramidal Syndrome (EPS),dystonia, restless legs syndrome (RLS) or periodic limb movement insleep (PLMS) in WO 05/044245, and have been disclosed as being useful inthe treatment of attention deficit hyperactivity disorder (ADHD) in WO02/055083.

EPS is a collective term for a series of adverse neurological reactionsassociated with the use of antipsychotic drugs. There are six differentcategories of EPS-related neurological syndromes of which four,dystonia, akathisia, pseudoparkinsonism (parkinsonian syndrome), andtardive dyskinesia, are particularly prevalent in patients takingantipsychotic medication. Dystonia is a painful spasm of the musclegroups of, in particular, the neck, jaw, back, pharynx, and larynx. Itis most common in young males being treated with antipsychotic drugs,but can also be associated with the use of cocaine, tricyclicantidepressants, lithium and anticonvulsants such as phenytoin andcarbamazepine. Pseudoparkinsonism manifests itself as akinesia(rigidity, stiffness and slow voluntary motion, stooped, shuffling walk)and tremor and these symptoms develop within weeks or months afterinitiation of therapy. Akathisia manifests itself as strong, subjectiveinner feelings of distress or discomfort characterized by motorrestlessness. Often mistaken for agitation or anxiety, this commonsyndrome is frequently under-diagnosed and is the least responsive totreatment. Tardive dyskinesia is a late-appearing syndrome associatedwith chronic use of neuroleptic drugs. It occurs more frequently inolder patients and is characterized by stereotypical, repetitive,involuntary, quick choreiform movements of the face, eyelids, mouth,tongue, extremities and trunk.

EPS is more prevalent with the use of typical antipsychotic agents buthas also been reported with the use of atypical agents. Typicalantipsychotics include loxapine, haloperidol, chlorpromazine,prochlorperazine and thiothixene. Atypical antipsychotics includeclozapine, olanzapine, loxapine, quetiapine, ziprasidone, risperidoneand aripiprazole.

Akathisia is also a characteristic of RLS and PLMS, as well as PLMD(periodic leg (or limb) movement disorder). RLS is a common disorderthat causes patients to have an irresistible and unpleasant desire tomove their legs; it usually manifests during periods of inactivityand/or at night, and can disturb sleep. Patients who do not have thetypical RLS symptoms, but who do exhibit periodic leg movements thatadversely impact sleep, are diagnosed with PLMS. Treatments for RLS andPLMS have included levodopa/carbidopa, levodopa/benserazide, dopamineagonists such as pramipexole and ropinerole, benzodiazepines, opioids,anticonvulsants and iron (ferrous sulfate). RLS and PLMS have beenextensively described in the literature, for example by Saletu et al,Neuropsychobiology, 41, 4 (2000), p. 190-9.

Some xanthine-related compounds have been found to be A₁ receptorselective antagonists, and xanthine and non-xanthine compounds have beenfound to have high A_(2a) affinity with varying degrees of A_(2a) vs. A₁selectivity. Triazolo-pyrimidine adenosine A_(2a) receptor antagonistshave been disclosed previously, for example in WO 95/01356; U.S. Pat.No. 5,565,460; WO 97/05138; WO 98/52568, U.S. Pat. No. 6,630,475, U.S.Pat. No. 6,653,315, U.S. Pat. No. 6,897,217 and PCT/US05/013454, filedApr. 19, 2005.

This invention is a selection invention over U.S. Pat. No. 6,897,217.

SUMMARY OF THE INVENTION

The present invention relates to the compound having the structuralformula I

or a pharmaceutically acceptable salt thereof.

Another aspect of the invention is a pharmaceutical compositioncomprising a therapeutically effective amount of the compound of formulaI in a pharmaceutically acceptable carrier.

Yet another aspect of the invention is a method of treating centralnervous system disorders including movement disorders, e.g., Parkinson'sDisease, Extra-Pyramidal Syndrome, restless legs syndrome, essentialtremor, Huntington's Disease, dystonia, periodic limb movement in sleep;attention disorders, e.g., attention deficit hyperactivity disorder,cognitive impairment and negative symptoms of schizophrenia; and toother central nervous system diseases such as depression, stroke andpsychoses, comprising administering the compound of formula I to amammal in need of such treatment.

In particular, the invention is drawn to the method of treating movementdisorders such as Parkinson's disease, essential tremor or Huntington'sDisease comprising administering the compound of formula I to a mammalin need of such treatment.

Still another aspect of the invention is a method of treatingParkinson's disease with a combination of the compound of formula I andone or more agents useful in the treatment of Parkinson's disease, forexample dopamine; L-DOPA; a dopaminergic agonist; an inhibitor ofmonoamine oxidase, type B (MAO-B); a DOPA decarboxylase inhibitor (DCI);or a catechol-O-methyltransferase (COMT) inhibitor. Also claimed is apharmaceutical composition comprising the compound of formula I and oneor more agents known to be useful in the treatment of Parkinson's in apharmaceutically acceptable carrier.

The invention also relates to the treatment or prevention of EPS (e.g.,dystonia, akathisia, pseudoparkinsonism and tardive dyskinesia)comprising administering the compound of formula I to a mammal in needof such treatment. In particular, this method is for the treatment orprevention of EPS in patients treated with an antipsychotic agent thathas the side effect of inducing EPS. The compound of formula I can beadministered after the symptoms of EPS have manifested, or the compoundof formula I can be administered at the onset of administering anantipsychotic agent in order to prevent EPS from occurring. Thus, theinvention also includes a method of treating or preventing EPS inducedby an antipsychotic agent comprising administering a combination of anantipsychotic agent and the compound of formula I to a patient in needthereof.

The invention also relates to the treatment of primary (idiopathic)dystonia, and to the treatment or prevention of dystonia in patients whoexhibit dystonia as a result of treatment with a tricyclicantidepressant, lithium or an anticonvulsant, or who have used cocaine,comprising administering a therapeutically effective amount of thecompound of formula I to a patient in need thereof. When dystonia iscaused by treatment with a tricyclic antidepressant, lithium or ananticonvulsant, the compound of formula I can be administered after thesymptoms of dystonia have manifested, or the compound of formula I canbe administered at the onset of administering a tricyclicantidepressant, lithium or an anticonvulsant in order to preventdystonia from occurring. The invention, therefore, also includes amethod of treating or preventing dystonia induced by a tricyclicantidepressant, lithium or an anticonvulsant comprising administering acombination of the compound of formula I and a tricyclic antidepressant,lithium or an anticonvulsant to a patient in need thereof.

The invention further relates to treatment of abnormal movementdisorders such as RLS or PLMS, comprising administering to a patient inneed thereof a therapeutically effective amount of the compound offormula I. The invention also comprises a method of treating RLS or PLMScomprising administering a combination of the compound of formula I withanother agent useful in treating RLS or PLMS, such aslevodopa/carbidopa, levodopa/benserazide, a dopamine agonist, abenzodiazepine, an opioid, an anticonvulsant or iron, to a patient inneed thereof.

The invention also relates to the treatment of attention relateddisorders such as attention deficit disorder (ADD) and ADHD, as well ascognitive impairment and negative symptoms of schizophrenia, comprisingadministering a therapeutically effective amount of the compound offormula I.

In another aspect, this invention relates to a kit comprising, inseparate containers in a single package, pharmaceutical compositions foruse in combination to treat Parkinson's Disease, wherein one containercomprises a pharmaceutical composition comprising an effective amount ofthe compound of formula I in a pharmaceutically acceptable carrier, andwherein a separate container comprises a pharmaceutical compositioncomprising an effective amount of an agent useful in the treatment ofParkinson's disease.

In another aspect, this invention relates to a kit comprising, inseparate containers in a single package, pharmaceutical compositions foruse in combination to treat or prevent EPS caused by treatment withantipsychotic agent, wherein one container comprises a pharmaceuticalcomposition comprising an effective amount of the compound of formula Iin a pharmaceutically acceptable carrier, and wherein a separatecontainer comprises a pharmaceutical composition comprising an effectiveamount of an antipsychotic agent.

In another aspect, this invention relates to a kit comprising, inseparate containers in a single package, pharmaceutical compositions foruse in combination to treat or prevent dystonia caused by treatment witha tricyclic antidepressant, lithium or an anticonvulsant, wherein onecontainer comprises a pharmaceutical composition comprising an effectiveamount of the compound of formula I in a pharmaceutically acceptablecarrier, and wherein a separate container comprises a pharmaceuticalcomposition comprising an effective amount of a tricyclicantidepressant, lithium or an anticonvulsant.

In another aspect, this invention relates to a kit comprising, inseparate containers in a single package, pharmaceutical compositions foruse in combination to treat RLS or PLMS, wherein one container comprisesa pharmaceutical composition comprising an effective amount of thecompound of formula I in a pharmaceutically acceptable carrier, andwherein a separate container comprises a pharmaceutical compositioncomprising an effective amount of levodopa/carbidopa,levodopa/benserazide, a dopamine agonist, a benzodiazepine, an opioid,an anticonvulsant or iron.

The invention also relates to the use of the compound of formula I forthe preparation of a medicament for treating or preventing Parkinson'sDisease, EPS, dystonia, RLS, PLMS, essential tremor, Huntington'sDisease, cognitive impairment or negative symptoms of schizophrenia,alone or in combination with the other agents discussed above.

DETAILED DESCRIPTION

As used herein, the term “composition” is intended to encompass aproduct comprising the specified ingredients in the specified amounts,as well as any product which results, directly or indirectly, fromcombination of the specified ingredients in the specified amounts.

Prodrugs and solvates of the compound of the invention are alsocontemplated herein. The term “prodrug”, as employed herein, denotes acompound that is a drug precursor which, upon administration to asubject, undergoes chemical conversion by metabolic or chemicalprocesses to yield a compound of formula I or a salt and/or solvatethereof. A discussion of prodrugs is provided in T. Higuchi and V.Stella, Pro-drugs as Novel Delivery Systems (1987) Volume 14 of theA.C.S. Symposium Series, and in Bioreversible Carriers in Drug Design,(1987) Edward B. Roche, ed., American Pharmaceutical Association andPergamon Press, both of which are incorporated herein by referencethereto.

“Solvate” means a physical association of a compound of this inventionwith one or more solvent molecules. This physical association involvesvarying degrees of ionic and covalent bonding, including hydrogenbonding. In certain instances the solvate will be capable of isolation,for example when one or more solvent molecules are incorporated in thecrystal lattice of the crystalline solid. “Solvate” encompasses bothsolution-phase and isolatable solvates. Non-limiting examples ofsuitable solvates include ethanolates, methanolates, and the like.“Hydrate” is a solvate wherein the solvent molecule is H₂O.

Polymorphic forms of the compound of formula I, and of the salts,solvates and prodrugs of the compound of formula I, are intended to beincluded in the present invention.

“Effective amount” or “therapeutically effective amount” is meant todescribe an amount of compound or a composition of the present inventioneffective as an adenosine A_(2a) receptor antagonist and thus producingthe desired therapeutic effect in a suitable patient.

“Patient” includes both human and animals.

“Mammal” means humans and other mammalian animals.

The compound of formula I forms salts that are also within the scope ofthis invention. Reference to the compound of formula I herein isunderstood to include reference to salts thereof, unless otherwiseindicated. The term “salt(s)”, as employed herein, denotes acidic saltsformed with inorganic and/or organic acids, as well as basic saltsformed with inorganic and/or organic bases. In addition, when thecompound of formula I contains both a basic moiety, such as, but notlimited to a pyridine or imidazole, and an acidic moiety, such as, butnot limited to a carboxylic acid, zwitterions (“inner salts”) may beformed and are included within the term “salt(s)” as used herein.Pharmaceutically acceptable (i.e., non-toxic, physiologicallyacceptable) salts are preferred, although other salts are also useful.Salts of the compounds of the formula I may be formed, for example, byreacting the compound of formula I with an amount of acid or base, suchas an equivalent amount, in a medium such as one in which the saltprecipitates or in an aqueous medium followed by lyophilization.

Exemplary acid addition salts include acetates, adipates, alginates,ascorbates, aspartates, benzoates, benzenesulfonates, bisulfates,borates, butyrates, citrates, camphorates, camphorsulfonates,cyclopentanepropionates, digluconates, dodecylsulfates,ethanesulfonates, fumarates, glucoheptanoates, glycerophosphates,hemisulfates, heptanoates, hexanoates, hydrochlorides, hydrobromides,hydroiodides, 2-hydroxyethanesulfonates, lactates, maleates,methanesulfonates, 2-naphthalenesulfonates, nicotinates, nitrates,oxalates, pectinates, persulfates, 3-phenylpropionates, phosphates,picrates, pivalates, propionates, salicylates, succinates, sulfates,sulfonates (such as those mentioned herein), tartrates, thiocyanates,toluenesulfonates (also known as tosylates,) undecanoates, and the like.Additionally, acids which are generally considered suitable for theformation of pharmaceutically useful salts from basic pharmaceuticalcompounds are known.

Exemplary basic salts include ammonium salts, alkali metal salts such assodium, lithium, and potassium salts, alkaline earth metal salts such ascalcium and magnesium salts, salts with organic bases (for example,organic amines) such as benzathines, dicyclohexylamines, hydrabamines(formed with N,N-bis(dehydro-abietyl)ethylenediamine),N-methyl-D-glucamines, N-methyl-D-glucamides, t-butyl amines, and saltswith amino acids such as arginine, lysine and the like. Basicnitrogen-containing groups may be quarternized with agents such as loweralkyl halides (e.g. methyl, ethyl, propyl, and butyl chlorides, bromidesand iodides), dialkyl sulfates (e.g. dimethyl, diethyl, dibutyl, anddiamyl sulfates), long chain halides (e.g. decyl, lauryl, myristyl andstearyl chlorides, bromides and iodides), aralkyl halides (e.g. benzyland phenethyl bromides), and others.

All such acid salts and base salts are intended to be pharmaceuticallyacceptable salts within the scope of the invention and all acid and basesalts are considered equivalent to the free forms of the correspondingcompounds for purposes of the invention.

Compounds of formula I, and salts, solvates and prodrugs thereof, mayexist in their tautomeric form (for example, as an amide or iminoether). All such tautomeric forms are contemplated herein as part of thepresent invention.

All stereoisomers (for example, geometric isomers, optical isomers andthe like) of the present compound (including those of the salts,solvates and prodrugs of the compound as well as the salts and solvatesof the prodrugs), such as those which may exist due to asymmetriccarbons on various substituents, including enantiomeric forms (which mayexist even in the absence of asymmetric carbons), rotameric forms,atropisomers, and diastereomeric forms, are contemplated within thescope of this invention. Individual stereoisomers of the compounds ofthe invention may, for example, be substantially free of other isomers,or may be admixed, for example, as racemates or with all other, or otherselected, stereoisomers. The chiral centers of the present invention canhave the S or R configuration as defined by the IUPAC 1974Recommendations. The use of the terms “salt”, “solvate” “prodrug” andthe like, is intended to equally apply to the salt, solvate and prodrugof enantiomers, stereoisomers, rotamers, tautomers, racemates orprodrugs of the inventive compounds.

The other agents known to be useful in the treatment of Parkinson'sdisease that can be administered in combination with the compounds offormula I include: L-DOPA; dopaminergic agonists such as quinpirole,ropinirole, pramipexole, pergolide and bromocriptine; MAO-B inhibitorssuch as deprenyl and selegiline; DOPA decarboxylase inhibitors such ascarbidopa and benserazide; and COMT inhibitors such as tolcapone andentacapone.

Antipsychotic agents causing the EPS treated by adenosine A_(2a)receptor antagonists and for use in combination with adenosine A_(2a)receptor antagonists include typical and atypical antipsychotic agents.Typical antipsychotics include loxapine, haloperidol, chlorpromazine,prochlorperazine and thiothixene. Atypical antipsychotics includeclozapine, olanzapine, loxapine, quetiapine, ziprasidone, risperidoneand aripiprazole.

Tricyclic antidepressants causing dystonia treated by adenosine A_(2a)receptor antagonists include perphenazine, amitriptyline, desipramine,doxepin, trimipramine and protriptyline. Anticonvulsants which may causedystonia, but which also may be useful in treating ERLS or PLMS includephenytoin, carbamazepine and gabapentin.

Dopamine agonists useful in treating RLS and PLMS include pergolide,pramipexole, ropinerole, fenoldopam and cabergoline.

Opioids useful in treating PRLS and PLMS include codeine, hydrocodone,oxycodone, propoxyphene and tramadol.

Benzodiazepines useful in treating PRLS and PLMS include clonazepam,triazolam and temazepam.

The antipsychotics, tricyclic antidepressants, anticonvulsants, dopamineagonists, opioids and benzodiazepines are commercially available and aredescribed in the literature, e.g., in The Physicians' Desk Reference(Montvale: Medical Economics Co., Inc., 2001).

It is contemplated that the compound of formula I could be administeredin combination with one or more other agents (e.g., antipsychotics,tricyclic antidepressants, anticonvulsants, dopamine agonists, opioidsor benzodiazepines), although administration of the compound of formulaI in combination with one other agent is preferred for each of theindications. While administration of separate dosage forms of thecompound of formula I and the other agent(s) are preferred, it is alsocontemplated that the other agent(s) could be combined in a singledosage form with the compound of formula I for the treatment orprevention of Parkinson's disease, EPS, dystonia, RLS or PLMS. It isalso contemplated that the compound of formula I could be administeredin combination with another adenosine A_(2a) antagonist.

Compounds of formula I can be prepared by known methods from startingmaterials either known in the art or prepared by methods known in theart; see, for example, U.S. Pat. No. 6,897,217.

Abbreviations used in the specification are as follows: Ac (acetyl); Me(methyl); Et (ethyl); Ph (phenyl); DMF (dimethylformamide); DIPEA(diisopropylethylamine); RT (room temperature).

Example 1

Step 1: A mixture of 4-fluoro-2-hydroxyacetophenone 1 (50 g, 324 mmol),hydroxylamine hydrochloride (45 g, 648 mmol), and sodium acetate (40 g,488 mmol) in anhydrous MeOH (1 L) was refluxed for 2 h. After cooling toRT, the reaction mixture was slowly poured onto ice and stirred for 30min. The white precipitate thus obtained was filtered through suctionand then dissolved in CH₂Cl₂, dried (MgSO₄), filtered, and concentratedto give 2 as a white solid (50 g, 91% yield) which was used withoutfurther purification for the next step.Step 2: To a solution of the oxime 2 (50 g, 296 mmol) in DMF (800 ml)was added sodium acetate (55 g, 670 mmol) followed by acetic anhydride(65 ml, 689 mmol). The reaction mixture was refluxed for 3-4 h, at whichstage all the starting material was consumed as indicated by TLC (10%EtOAc in hexanes). After cooling to RT, the reaction mixture was pouredinto water and extracted several times with ether. The combined organicfractions were washed with brine, dried (Na₂SO₄), filtered andconcentrated to give 3 as a brownish solid (42 g, 94% yield).Step 3: To an ice-cold solution of 3 (42 g, 278 mmol) in conc. H₂SO₄(300 ml) was added dropwise conc. HNO₃ (70 ml) through an additionfunnel. After the addition was complete, the reaction mixture was warmedto RT and stirred for 2-3 h. After the starting material was consumed asindicated by TLC (10% EtOAc in hexanes), the reaction mixture was pouredslowly on ice with constant shaking. The resulting solid was filtered,dissolved in CH₂Cl₂ and washed with saturated aq. NaHCO₃ solution andbrine. The combined organic fractions were dried over MgSO₄, filtered,and concentrated to give 47 g (86% yield) of 4 as a yellow solid.Step 4: A solution of 4 (47 g, 240 mmol) in AcOH (800 ml) was warmed to40° C. and to this warm solution was added a solution of SnCl₂-H₂O (150g, 665 mmol) in conc. HCl (400 ml). The reaction mixture was refluxedfor 2 h and then cooled to RT. The pH was carefully adjusted to 5-6 withaqueous NaOH to precipitate most of the tin salts and then ether wasadded to the mixture with constant stirring. After decanting the liquid,the organic layer was separated and the aqueous layer was back extractedseveral times with ether. The combined organic fractions were washedwith brine, dried (Na₂SO₄), filtered and concentrated to give a brownoil. Purification by column chromatography (10-20% EtOAc in hexanes)gave 22 g (55% yield) of 5 as a yellow solid.Step 5: A solution of 5 (3.2 g, 19 mmol) in CH₂Cl₂ (100 ml) was treatedwith 2M HCl/ether (9.6 ml, 19 mmol) and the solvent was removed underreduced pressure. The white solid was taken in chlorobenzene (80 ml) andtreated with bis(chloroethyl)-amine (3.8 g, 21 mmol). The reactionmixture was refluxed for 48 h, at which stage most of the startingmaterial was consumed. Most of the solvent was removed under reducedpressure and the residue was taken up in hot MeOH (200 ml). The blackinsoluble residue was filtered off and the filtrate was purified bycolumn chromatography (2-5% 7N NH₃-MeOH in CH₂Cl₂) to give 2.6 g (57%yield) of 6.Step 6: A mixture of 6 (2.6 g, 11 mmol), 7 (3.2 g, 12 mmol), KI (2.0 g,12 mmol), and DIPEA (2.3 ml, 13.3 mmol) in DMF (30 ml) was heated at110° C. for 48 h. After cooling to RT, water was added and the resultingsolid was filtered. The solid residue was dissolved in 10% MeOH—CH₂Cl₂,dry loaded on a silica gel column, and purified (2% MeOH in CH₂Cl₂)giving 2.7 g (52% yield) of the title compound. LCMS: 475 (M+H),purity=100%.

Because of its adenosine A_(2a) receptor antagonist activity, thecompound of the present invention is useful in the treatment of centralnervous system diseases such as Parkinson's Disease, Extra-PyramidalSyndrome, restless legs syndrome, essential tremor, Huntington'sDisease, attention deficit hyperactivity disorder, cognitive impairment,negative symptoms of schizophrenia, depression, stroke or psychoses. Inparticular, the compound of the present invention can improvemotor-impairment due to neurodegenerative diseases such as Parkinson'sdisease.

The pharmacological activity of the compound of the invention wasdetermined by the following in vitro and in vivo assays to measureA_(2a) receptor activity.

Human Adenosine A_(2a) and A₁ Receptor Competition Binding AssayProtocol

Membrane Sources:

A_(2a): Human A_(2a) Adenosine Receptor membranes, Catalog #RBHA2AM,Perkin Elmer Life Sciences, Shelton Conn. Dilute to 17 μg/100 μl inmembrane dilution buffer (see below).

Assay Buffers:

Membrane dilution buffer: Dulbecco's Phosphate Buffered Saline(Gibco/BRL)+10 mM MgCl₂.

Compound Dilution Buffer: Dulbecco's Phosphate Buffered Saline(Gibco/BRL)+10 mM MgCl₂ supplemented with 1.6 mg/ml methyl cellulose and16% DMSO. Prepared fresh daily.

Ligands:

A_(2a): [3H]-SCH 58261, custom synthesis, AmershamPharmacia Biotech,Piscataway, N.J. Stock is prepared at 1 nM in membrane dilution buffer.Final assay concentration is 0.5 nM.

A₁: [3H]-DPCPX, AmershamPharmacia Biotech, Piscataway, N.J. Stock isprepared at 2 nM in membrane dilution buffer. Final assay concentrationis 1 nM.

Non-Specific Binding:

A_(2a): To determine non-specific binding, add 100 nM CGS 15923 (RBI,Natick, Mass.). Working stock is prepared at 400 nM in compound dilutionbuffer.

A₁: To determine non-specific binding, add 100 μM NECA (RBI, Natick,Mass.). Working stock is prepared at 400 μM in compound dilution buffer.

Compound Dilution:

Prepare 1 mM stock solutions of compounds in 100% DMSO. Dilute incompound dilution buffer. Test at 10 concentrations ranging from 3 μM to30 pM. Prepare working solutions at 4× final concentration in compounddilution buffer.

Assay Procedure:

Perform assays in deep well 96 well plates. Total assay volume is 200μl. Add 50 μl compound dilution buffer (total ligand binding) or 50 μlCGS 15923 working solution (A_(2a) non-specific binding) or 50 μl NECAworking solution (A₁ non-specific binding) or 50 μl of drug workingsolution. Add 50 μl ligand stock ([3H]-SCH 58261 for A_(2a), [3H]-DPCPXfor A₁). Add 100 μl of diluted membranes containing the appropriatereceptor. Mix. Incubate at room temperature for 90 minutes. Harvestusing a Brandel cell harvester onto Packard GF/B filter plates. Add 45μl Microscint 20 (Packard), and count using the Packard TopCountMicroscintillation Counter. Determine IC₅₀ values by fitting thedisplacement curves using an iterative curve fitting program (Excel).Determine K_(i) values using the Cheng-Prusoff equation.

Haloperidol-Induced Catalepsy in the Rat

Male Sprague-Dawley rats (Charles River, Calco, Italy) weighing 175-200g are used. The cataleptic state is induced by the subcutaneousadministration of the dopamine receptor antagonist haloperidol (1 mg/kg,sc), 90 min before testing the animals on the vertical grid test. Forthis test, the rats are placed on the wire mesh cover of a 25×43plexiglass cage placed at an angle of about 70 degrees with the benchtable. The rat is placed on the grid with all four legs abducted andextended (“frog posture”). The use of such an unnatural posture isessential for the specificity of this test for catalepsy. The time spanfrom placement of the paws until the first complete removal of one paw(descent latency) is measured maximally for 120 sec.

The selective A_(2A) adenosine antagonists under evaluation areadministered orally at doses ranging between 0.03 and 3 mg/kg, 1 and 4 hbefore scoring the animals.

In separate experiments, the anticataleptic effects of the referencecompound, L-DOPA (25, 50 and 100 mg/kg, ip), were determined.

6-OHDA Lesion of the Middle Forebrain Bundle in Rats

Adult male Sprague-Dowley rats (Charles River, Calco, Como, Italy),weighing 275-300 g, are used in all experiments. The rats are housed ingroups of 4 per cage, with free access to food and water, undercontrolled temperature and 12 hour light/dark cycle. The day before thesurgery the rats are fasted over night with water ad libitum.

Unilateral 6-hydroxydopamine (6-OHDA) lesion of the middle forebrainbundle is performed according to the method described by Ungerstedt etal. (Brain Research, 1971, 6-OHDA and Cathecolamine Neurons, NorthHolland, Amsterdam, 101-127), with minor changes. Briefly, the animalsare anaesthetized with chloral hydrate (400 mg/kg, ip) and treated withdesipramine (10 mpk, ip) 30 min prior to 6-OHDA injection in order toblock the uptake of the toxin by the noradrenergic terminals. Then, theanimals are placed in a stereotaxic frame. The skin over the skull isreflected and the stereotaxic coordinates (−2.2 posterior from bregma(AP), +1.5 lateral from bregma (ML), 7.8 ventral from dura (DV) aretaken, according to the atlas of Pellegrino et al (Pellegrino L. J.,Pellegrino A. S. and Cushman A. J., A Stereotaxic Atlas of the RatBrain, 1979, New York: Plenum Press). A burr hole is then placed in theskull over the lesion site and a needle, attached to a Hamilton syringe,is lowered into the left MFB. Then 8 μg 6-OHDA-HCl is dissolved in 4 μlof saline with 0.05% ascorbic acid as antioxidant, and infused at theconstant flow rate of 1 μl/1 min using an infusion pump. The needle iswithdrawn after additional 5 min and the surgical wound is closed andthe animals left to recover for 2 weeks.

Two weeks after the lesion the rats are administered with L-DOPA (50mg/kg, ip) plus Benserazide (25 mg/kg, ip) and selected on the basis ofthe number of full contralateral turns quantified in the 2 h testingperiod by automated rotameters (priming test). Any rat not showing atleast 200 complete turns/2 h is not included in the study.

Selected rats receive the test drug 3 days after the priming test(maximal dopamine receptor supersensitivity). The new A_(2A) receptorantagonist is administered orally at dose levels ranging between 0.1 and3 mg/kg at different time points (i.e., 1, 6, 12 h) before the injectionof a subthreshold dose of L-DOPA (4 mpk, ip) plus benserazide (4 mpk,ip) and the evaluation of turning behavior.

EPS Assay

The following procedure describes the use of an adenosine A_(2a)antagonist to attenuate the Extra-Pyramidal Syndrome (EPS) displayed incebus apella monkeys sensitized to the dopamine D₂ receptor antagonist,haloperidol.

A colony of Cebus apella monkeys previously sensitized to the chroniceffects of haloperidol exhibits EPS when administered haloperidolacutely (0.3 mg/kg, p.o.). A test compound is administered orally (p.o.)at a dose ranging from 0.3-30 mg/kg, in conjunction with haloperidol.The studies are conducted using a within-subjects design such that eachmonkey receives all treatments (vehicle and doses of test compound) in acrossover, balanced design. The reduction in the maximum EPS score, aswell as the dose-dependent delay in the onset of EPS are determined.

Clinical guidelines for the treatment of RLS and PLMS have beenestablished: see A. L. Chesson et al, Sleep, 22, 7 (1999), p. 961-8.Efficacy of adenosine A_(2a) antagonists in treating RLS and PLMS can bedetermined by a method analogous to the clinical method described in theliterature for pramipexole and ropinerole by Weimerskirch et al, Annalsof Pharmacotherapy, 35, 5 (2001), p. 627-30.

Using the above test procedures, the following results were obtained forthe compound of the invention.

Results of the binding assay on the compound of the invention showed anA_(2a)K_(i) value of 0.43 nM.

Selectivity is determined by dividing K_(i) for A₁ receptor by K_(i) forA_(2a) receptor. The compound of the invention has a selectivity greaterthan 2500 fold.

In the 6-OHDA lesion test, test animals administered a combination of acompound of formula I and a sub-threshold amount of L-DOPA demonstratedsignificantly higher contralateral turning:

-   -   L-DOPA: 171±47 rotations    -   0.1 mpk: 218±142 rotations    -   0.3 mpk: 406±167 rotations    -   1 mpk: 360±178 rotations    -   3 mpk: 403±125 rotations

In the haloperidol-induced catalepsy assay in rats @ 4 h, the %inhibition was as follows:

-   -   0.3 mpk: 28% inhibition of catalepsy    -   1 mpk: 47% inhibition of catalepsy    -   3 mpk: 53% inhibition of catalepsy

In the EPS assay, four haloperidol-sensitized monkeys wereco-administered the compound of formula I (30 mg/kg) and haloperidol(0.3 mg/kg) in a banana. A scoring system to rate the severity of eachsymptom was employed over a 6 hour observation period. The compound offormula I completely blocked haloperidol-induced EPS in three subjectsduring the 6 hr observation period and in the fourth subject, delayedonset and reduced severity of EPS compared to that observed in monkeysdosed with haloperidol alone.

Ex Vivo Binding Study to Show Duration of Receptor Occupancy:

Rats were dosed with 1 mg/kg of the compound of formula I and thecompound of formula II (generically disclosed in U.S. Pat. No.6,897,217)

for 4, 8, 12, and 16 hours prior to sacrifice and removal of brains. TheA_(2a) receptor-rich striatal nucleus was dissected and homogenized inbuffer solution. Striatal homogenate was incubated with the A_(2a)antagonist radioligand ³H-SCH 58261 (see WO 96/38728) prior toseparation of bound and free radioactivity by filtration. Boundradioligand on filters was dried, soaked with scintillation fluid, andcounted. Homogenates from striata of vehicle-treated rats treated withthe same experimental conditions defined the quantity of boundradioligand in the absence of test compound.

For both compounds, receptors are occupied by test compounds at 4 hours,demonstrated by the decrease (42 and 47%) in ³H-SCH 58261 binding.However, in striatal homogenates from rats dosed with formula II,radioligand binding is restored to near vehicle-treated levels at 8hours, indicating that test compound is no longer competing for A_(2a)receptors at that time. The compound of formula I exhibits sustaineddisplacement of radioligand through 12 hours (40% displacement ofradiolabel).

For preparing pharmaceutical compositions from the compound of thisinvention, inert, pharmaceutically acceptable carriers can be eithersolid or liquid. Solid form preparations include powders, tablets,dispersible granules, capsules, cachets and suppositories. The powdersand tablets may be comprised of from about 5 to about 70 percent activeingredient. Suitable solid carriers are known in the art, e.g. magnesiumcarbonate, magnesium stearate, talc, sugar, lactose. Tablets, powders,cachets and capsules can be used as solid dosage forms suitable for oraladministration.

For preparing suppositories, a low melting wax such as a mixture offatty acid glycerides or cocoa butter is first melted, and the activeingredient is dispersed homogeneously therein as by stirring. The moltenhomogeneous mixture is then poured into convenient sized molds, allowedto cool and thereby solidify.

Liquid form preparations include solutions, suspensions and emulsions.As an example may be mentioned water or water-propylene glycol solutionsfor parenteral injection.

Liquid form preparations may also include solutions for intranasaladministration.

Aerosol preparations suitable for inhalation may include solutions andsolids in powder form, which may be in combination with apharmaceutically acceptable carrier, such as an inert compressed gas.

Also included are solid form preparations which are intended to beconverted, shortly before use, to liquid form preparations for eitheroral or parenteral administration. Such liquid forms include solutions,suspensions and emulsions.

The compound of the invention may also be deliverable transdermally. Thetransdermal compositions can take the form of creams, lotions, aerosolsand/or emulsions and can be included in a transdermal patch of thematrix or reservoir type as are conventional in the art for thispurpose.

Preferably the compound is administered orally.

Preferably, the pharmaceutical preparation is in unit dosage form. Insuch form, the preparation is subdivided into unit doses containingappropriate quantities of the active component, e.g., an effectiveamount to achieve the desired purpose.

The quantity of active compound of formula I in a unit dose ofpreparation may be varied or adjusted from about 0.1 mg to 1000 mg, morepreferably from about 1 mg to 300 mg, according to the particularapplication.

The actual dosage employed may be varied depending upon the requirementsof the patient and the severity of the condition being treated.Determination of the proper dosage for a particular situation is withinthe skill of the art. Generally, treatment is initiated with smallerdosages which are less than the optimum dose of the compound.Thereafter, the dosage is increased by small increments until theoptimum effect under the circumstances is reached. For convenience, thetotal daily dosage may be divided and administered in portions duringthe day if desired.

The amount and frequency of administration of the compound of theinvention and the pharmaceutically acceptable salts thereof will beregulated according to the judgment of the attending clinicianconsidering such factors as age, condition and size of the patient aswell as severity of the symptoms being treated. A typical recommendeddosage regimen for the compound of formula I is oral administration offrom 10 mg to 2000 mg/day preferably 10 to 1000 mg/day, in two to fourdivided doses to provide relief from central nervous system diseasessuch as Parkinson's disease or the other disease or conditions listedabove.

The doses and dosage regimen of the other agents used in combinationwith the compound of formula I, i.e., the Parkinson's Disease agents,the antipsychotics, tricycicic antidepressants, anticonvulsants,dopamine agonists, benzodiazepines, opioids, lithium or iron, will bedetermined by the attending clinician in view of the approved doses anddosage regimen in the package insert, taking into consideration the age,sex and condition of the patient and the severity of the disease. Whenadministered in combination, the compound of formula I and the otheragent can be administered simultaneously or sequentially. This isparticularly useful when the components of the combination arepreferably given on different dosing schedules, e.g., one component isadministered daily and the other every six hours, or when the preferredpharmaceutical compositions are different, e.g. one is preferably atablet and one is a capsule. It is therefore advantageous to provide thecompound of formula I and the other agent in a kit comprising, inseparate containers in a single package, pharmaceutical compositions foruse in combination to treat or prevent Parkinson's disease, EPS,dystonia, RLS or PLMS, wherein one container comprises a pharmaceuticalcomposition comprising an effective amount of a compound of formula I ina pharmaceutically acceptable carrier, and wherein a separate containercomprises a pharmaceutical composition comprising an effective amount ofanother agent appropriate to treat the indicated condition.

Those skilled in the art will recognize that a dosage form for one ofthe components of the combination can be modified to contain both thecompound of formula I and another agent, e.g., the compound of formula Iand an antipsychotic or the compound of formula I and a dopamineagonist.

While the present invention has been described in conjunction with thespecific embodiments set forth above, many alternatives, modificationsand variations thereof will be apparent to those of ordinary skill inthe art. All such alternatives, modifications and variations areintended to fall within the spirit and scope of the present invention.

1. A compound having the structural formula

or a pharmaceutically acceptable salt thereof.
 2. A pharmaceuticalcomposition comprising a therapeutically effective amount of a compoundof claim 1 in a pharmaceutically acceptable carrier.
 3. A pharmaceuticalcomposition comprising a therapeutically effective amount of acombination of the compound of claim 1, and 1 to 3 other agents usefulin treating Parkinson's disease in a pharmaceutically acceptablecarrier.
 4. The composition of claim 3 wherein said other agents areindependently L-DOPA, dopaminergic agonists, MAO-B inhibitors, DOPAdecarboxylase inhibitors or COMT inhibitors.